U.S. patent application number 11/770250 was filed with the patent office on 2007-11-22 for iron phosphating process that reduces laser scale resulting in improved paint adhesion.
This patent application is currently assigned to Henkel Kommanditgesellschaft auf Aktien (Henkel KGaA). Invention is credited to Daniel A. Service.
Application Number | 20070267106 11/770250 |
Document ID | / |
Family ID | 36615235 |
Filed Date | 2007-11-22 |
United States Patent
Application |
20070267106 |
Kind Code |
A1 |
Service; Daniel A. |
November 22, 2007 |
Iron Phosphating Process That Reduces Laser Scale Resulting In
Improved Paint Adhesion
Abstract
A process for iron phosphating ferrous metal substrates having
undesirable ferrous oxides thereon, such as that formed by laser
cutting, that eliminates at least the pickling step in the
phosphating process and provides good paint adhesion, and
compositions of matter useful in the process.
Inventors: |
Service; Daniel A.; (Dundas,
CA) |
Correspondence
Address: |
HENKEL CORPORATION
THE TRIAD, SUITE 200
2200 RENAISSANCE BLVD.
GULPH MILLS
PA
19406
US
|
Assignee: |
Henkel Kommanditgesellschaft auf
Aktien (Henkel KGaA)
Duesseldorf
DE
|
Family ID: |
36615235 |
Appl. No.: |
11/770250 |
Filed: |
June 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/US04/43937 |
Dec 28, 2004 |
|
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11770250 |
Jun 28, 2007 |
|
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Current U.S.
Class: |
148/253 ;
148/28 |
Current CPC
Class: |
C04B 28/34 20130101;
C23C 22/08 20130101; C23C 22/36 20130101; C04B 24/04 20130101; C04B
22/124 20130101; C04B 24/127 20130101; C04B 2103/40 20130101; C04B
22/124 20130101; C04B 2103/10 20130101; C04B 24/04 20130101; C04B
22/126 20130101; C04B 2103/0086 20130101; C04B 24/20 20130101; C04B
2103/0086 20130101; C04B 24/38 20130101; C04B 22/085 20130101; C04B
22/068 20130101; C04B 2103/0086 20130101; C04B 24/10 20130101; C04B
24/122 20130101; C04B 2103/44 20130101; C04B 2103/40 20130101; C04B
2103/40 20130101; C04B 2103/0086 20130101; C04B 24/04 20130101;
C04B 24/38 20130101; C04B 22/124 20130101; C04B 24/127 20130101;
C04B 24/10 20130101; C04B 24/122 20130101; C04B 24/04 20130101;
C04B 2103/0094 20130101; C04B 22/068 20130101; C04B 24/122
20130101; C04B 2103/44 20130101; C04B 24/20 20130101; C04B 22/068
20130101; C04B 2103/0094 20130101; C04B 24/20 20130101; C04B 22/126
20130101; C04B 22/126 20130101; C04B 2103/40 20130101; C04B 22/126
20130101; C04B 24/10 20130101; C04B 28/342 20130101; C04B
2111/00482 20130101; C04B 2111/00732 20130101; C04B 28/34 20130101;
C04B 28/34 20130101; C04B 28/342 20130101; C04B 28/342 20130101;
C23C 22/10 20130101 |
Class at
Publication: |
148/253 ;
148/028 |
International
Class: |
C23C 22/07 20060101
C23C022/07 |
Claims
1. A liquid concentrate composition of matter that when mixed with
9 times its own mass of water is a solution that forms a phosphate
conversion coating on a solid metal substrate with which it is
contacted, said concentrate composition comprising water and: (A) a
component of dissolved phosphate anions in an amount sufficient to
form the phosphate conversion coating on the substrate from a
working composition made by diluting the concentrate composition
with water only; (B) a component of sufficient dissolved acid to
give the concentrate composition itself and a working composition
made by diluting the concentrate composition with water only, an
acidic pH value and at least 20 points total acid; (C) a component
of dispersed aromatic carboxylic acid in an amount sufficient for
the working composition to protect the phosphated substrate against
flash rusting; and (D) a component of viscosity increasing agent
that is not part of any of components (A) through (C) as recited
immediately above.
2. The liquid concentrate composition of claim 1 further comprising
at least one member selected from the group consisting of: (E) a
component of phosphating accelerator that is not part of any of
components (A) through (D); (F) a component of dissolved fluoride
ions that is not part of any of components (A) through (E); (G) a
component of chelating agent that is not part of compounds (A)
through (F); (H) a component of acidity adjustment agent that is
not part of any of components (A) to (G); and (J) a component of
one or more surfactants that is not part of any of components (A)
through (H).
3. The liquid concentrate composition of claim 1 comprising: (A)
15% to 60% by weight dissolved phosphate ions; based on a
stoichiometric equivalent as H.sub.3PO.sub.4; (B) 20 to 50 points
of total acid when diluted to working strength; (C) 0.5% to 10.0%
of at least one aromatic carboxylic acid containing from 7 to 20
carbon atoms; (D) 0.05 to 1.5% of xanthan gum or optionally a
viscosity modifying agent other than xanthan gum used in a
concentration to produce a same "static" viscosity of the
composition as the above stated amounts of xanthan gum; and (E) a
phosphating accelerator in an amount sufficient to provide a
working solution with a concentration of at least one member
selected from the group consisting of 6 ppt to 80 ppt of chlorate
ions, 1.0 ppt to 40 ppt of m-nitrobenzene sulfonate ions, 1 ppt to
40 ppt of m-nitrobenzoate ions, 1.0 ppt to 40 ppt of p-nitrophenol,
0.10 ppt to 3.0 ppt of hydrogen peroxide in free or bound form, 0.4
ppt to 50 ppt of hydroxylamine in free or bound form, 2.0 ppt to
100 ppt of a reducing sugar and 20 ppt to 600 ppt of nitrate
ions.
4. The liquid concentrate composition of claim 3 wherein component
(E) comprises at least two subcomponents (E.1) and (E.2) wherein
(E.1) comprises a water soluble source of hydroxylamine and (E.2)
comprises at least one nitroaromatic organic compound.
5. The liquid concentrate composition of claim 3 further
comprising: (F) at least one member selected from the group
consisting of 0.1% to 10% of uncomplexed fluoride, 0.1 to 8.5% of
complexed fluoride and mixtures thereof and wherein when both
uncomplexed fluoride and complexed fluoride are present the ratio
of uncomplexed fluoride to complexed fluoride is from 0.1:1.00 to
8.1.00 and when only uncomplexed fluoride or complexed fluoride is
present the total fluoride content of the composition is from 0.50%
to 8%.
6. The liquid concentrate of claim 3 further comprising: (G) from
0.02% to 1.0% of a chelating agent wherein the concentration is
measured as its stoichiometric equivalent as gluconic acid.
7. The composition of claim 3 further comprising: (H) 1% to 15% of
an acidity adjustment agent.
8. The composition of claim 3 further comprising: (J) at least one
surfactant.
9. The liquid concentrate composition of claim 1 comprising: (B) a
component of sufficient dissolved acid to give the concentrate
composition itself and a working composition made by diluting the
concentrate composition with water only, an acidic pH value of 3.5
or less and to give the working composition 20 to 50 points of
total acid when diluted to working strength.
10. The liquid concentrate of claim 3 comprising: (A) 15% to 50% by
weight dissolved phosphate ions based on the stoichiometric
equivalent as H.sub.3PO.sub.4; (B) 20 to 40 points of total acid
when diluted to working strength; (C) 1.5% to 6% of the at least
one aromatic carboxylic acid containing from 7 to 20 carbon atoms;
and (D) 0.20% to 1.0% of xanthan gum or optionally a viscosity
modifying agent other than xanthan gum used in a concentration to
produce the same static viscosity of the composition as the above
stated amounts of xanthan gum.
11. The liquid concentrate of claim 5 further comprising: (G) from
0.02% to 1% of a chelating agent wherein the concentration is
measured as its stoichiometric equivalent as gluconic acid.
12. The liquid concentrate of claim 11 further comprising: (H) 1%
to 15% of an acidity adjusting agent.
13. The liquid concentrate of claim 12 further comprising: (J) at
least one surfactant.
14. A process for treating a ferrous metal workpiece having laser
scale and /or other ferrous oxide on at least a portion of the
workpiece comprising: a) contacting a ferrous metal workpiece, in
the absence of a separate acid pickling pretreatment, with a
treatment solution comprising: (A) a component of dissolved
phosphate anions in an amount sufficient to form the phosphate
conversion coating on the substrate; (B) a component of sufficient
dissolved acid to give the working composition an acidic pH value
and 20 to 60 points total acid; (C) a component of dispersed
aromatic carboxylic acid in an amount sufficient for the working
composition to protect the phosphated substrate against flash
rusting; and (D) optionally, a component of viscosity increasing
agent that is not part of any of components (A) through (C) as
recited immediately above; at a sufficient temperature and a
sufficient time such that said oxide and/or scale on the workpiece
are reduced in amount and an iron phosphate coating is deposited on
the workpiece; and b) rinsing the coated ferrous metal substrate
with water.
15. The process of claim 14 wherein the working phosphating
composition comprises: (A) 1.5% to 10% by weight dissolved
phosphate ions; based on a stoichiometric equivalent as H.sub.3
PO.sub.4; (B) 20 to 50 points of total acid; and (C) 0.05% to 1.0%
of at least one aromatic carboxylic acid containing from 7 to 20
carbon atoms; and further comprises at least one member selected
from the group consisting of: (D) 0.01 to 1.5% of xanthan gum or
optionally a viscosity modifying agent other than xanthan gum used
in a concentration to produce a same "static" viscosity of the
composition as the above stated amounts of xanthan gum; (E) a
component of phosphating accelerator that is not part of any of
components (A) through (D); (F) a component of dissolved fluoride
ions that is not part of any of components (A) through (E); (G) a
component of chelating agent that is not part of compounds (A)
through (F); (H) a component of acidity adjustment agent that is
not part of any of components (A) to (G); and (J) a component of
one or more surfactants that is not part of any of components (A)
through (H).
16. A working phosphating composition that reduces laser scale
and/or ferrous oxides on a ferrous metal substrate and forms a
phosphate conversion coating on the ferrous metal substrate with
which it is contacted, in a single step, said concentrate
composition comprising water and: (A) 1.5% to 10% by weight
dissolved phosphate ions; based on a stoichiometric equivalent as
H.sub.3PO.sub.4; (B) 20 to 50 points of total acid; (C) 0.05% to
1.0% of at least one aromatic carboxylic acid containing from 7 to
20 carbon atoms; and further comprises at least one member selected
from the group consisting of: (D) 0.01 to 1.5% of xanthan gum or
optionally a viscosity modifying agent other than xanthan gum used
in a concentration to produce a same "static" viscosity of the
composition as the above stated amounts of xanthan gum; and (E) a
phosphating accelerator in an amount sufficient to provide a
working solution with a concentration of at least one member
selected from the group consisting of 0.6 ppt to 8.0 ppt of
chlorate ions, 0.10 ppt to 4.0 ppt of m-nitrobenzene sulfonate
ions, 0.10 ppt to 4.0 ppt of m-nitrobenzoate ions, 0.10 ppt to 4.0
ppt of p-nitrophenol, 0.01 ppt to 0.30 ppt of hydrogen peroxide in
free or bound form, 0.04 ppt to 5.0 ppt of hydroxylamine in free or
bound form, 0.20 ppt to 10.0 ppt of a reducing sugar and 2.0 ppt to
60.0 ppt of nitrate ions.
17. The working phosphating composition of claim 16 which further
comprises at least one member selected from the group consisting
of: (F) a component of dissolved fluoride ions that is not part of
any of components (A) through (E); (G) a component of chelating
agent that is not part of compounds (A) through (F); (H) a
component of acidity adjustment agent that is not part of any of
components (A) to (G); and (J) a component of one or more
surfactants that is not part of any of components (A) through
(H).
18. The working phosphating composition of claim 16 wherein
component (E) comprises at least two subcomponents (E.1) and (E.2)
wherein (E.1) comprises a water soluble source of hydroxylamine and
(E.2) comprises at least one nitroaromatic organic compound.
19. The working phosphating composition of claim 16 which further
comprises: (F) at least one member selected from the group
consisting of 0.01% to 1.0% of uncomplexed fluoride, 0.01 to 0.85%
of complexed fluoride and mixtures thereof and wherein when both
uncomplexed fluoride and complexed fluoride are present the ratio
of uncomplexed fluoride to complexed fluoride is from 0.1:1.00 to
8.1.00 and when only uncomplexed fluoride or complexed fluoride is
present the total fluoride content of the composition is from
0.050% to 0.8%. (G) from 0.02% to 1.0% of a chelating agent wherein
the concentration is measured as its stoichiometric equivalent as
gluconic acid; and (H) 0.1% to 1.5% of an acidity adjustment
agent.
20. The working phosphating composition of claim 17 having a pH of
less than 3 and a 25-45 total acid points.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation under 35 U.S.C. .sctn.
365(c) and .sctn.120 of International Application No.
PCT/US2004/043937, filed Dec. 28, 2004 and published in English as
WO 2006/071226A1 on Jul. 6, 2006.
FIELD OF THE INVENTION
[0002] This invention relates to an improved process for iron
phosphating ferrous metal substrates, preferably substrates having
scale such as that formed by laser cutting, that eliminates at
least the pickling step in the phosphating process and provides
good paint adhesion and compositions of matter useful in the
process.
BACKGROUND OF THE INVENTION
[0003] This invention relates to the well known general field of
phosphate conversion coating of metals, particularly to the type of
phosphate conversion coating known as iron side or non-crystalline
conversion coating that is formed on predominantly ferriferous
surfaces from a working phosphating composition that does not
contain any substantial amount of any divalent cations that form
insoluble phosphates, for example, zinc, nickel, cobalt, manganese,
calcium, magnesium, or the like. For brevity hereinafter, this type
of coating or type of composition for forming such a coating is
called simply iron phosphate or a grammatical variation
thereof.
[0004] In the automotive and industrial vehicle industry, metal
parts are often cut and shaped prior to painting. In prior art
processes for cutting metal, the cutting tool was typically a CNC
machine or the like which cuts the metal by mechanical means, that
is physical contact between the cutting tool and the workpiece to
be cut. This method of cutting resulted in minimal scale or oxide
being generated on the cut edge of the workpiece. The small amounts
of scale and oxide enabled the manufacturer to phosphate and paint
the workpiece after cutting with few paint adhesion problems,
without additional steps to remove the scale and oxide. Thus,
certain industries have developed processes and production lines
that have no provision for removal of scale between the cutting
stage and the phosphating stage.
[0005] With the introduction of laser forming and cutting of
workpieces, a new problem of laser generated scale and oxide on the
cut edge of workpieces arose. Manufacturers found that cutting
ferrous metal with lasers resulted in sufficient scale and oxide
formation at the cut edge of the workpiece to interfere with
adhesion of subsequently applied paint layers and the corrosion
resistance of the painted substrate. The poor paint adhesion caused
appearance problems such as a "ribboning effect", as well as
susceptibility to corrosion that was unacceptable to the
manufacturers. Conventional phosphating, typically zinc
phosphating, previously used as a treatment when mechanical cutting
means were used, did not improve the paint adhesion on the laser
cut edges enough to meet manufacturing requirements.
[0006] One attempted solution to poor paint adhesion on laser cut
edges was to pickle and oil the workpieces after cutting and prior
to phosphating. However, this method required the addition of a new
step and its attendant costs to the processing of the metal pieces.
The additional step requires equipment, skilled workers as well as
floor space or transport that had not been part of the economics of
manufacturing the metal parts when mechanical cutting was used.
Also, pickling solutions are typically strongly acidic solutions
and can be hazardous for workers and the environment. Due to the
nature of the chemicals involved in pickling, typically sulfuric
acid or nitric acid, there are also environmental and waste
disposal issues that must be addressed if a manufacturer chooses to
use this method. Thus, particularly for manufacturers who had no
need to pickle prior to the introduction of laser cutting, it is
desirable to provide a treatment that enhances the adhesion of
paint to the laser cut workpieces without the addition of new steps
or significant extra costs.
[0007] Iron phosphating processes for treatment of metal are known
in the art. Another attempted solution to the paint adhesion
problems caused by scale and oxide generated by laser cutting was
to replace the zinc phosphating treatment used prior to painting in
the prior art process with an iron phosphating treatment. However,
conventional iron phosphating treatments alone, typically having
pHs of 3.0 or more and total acid points of 6 to 14 did not provide
sufficient improvement to paint adhesion.
SUMMARY OF THE INVENTION
[0008] In attempting to solve the afore-mentioned problems,
Applicant developed a process for treating ferrous metal workpieces
having laser scale and/or other ferrous oxides, on at least the cut
edges of the workpiece that eliminates the need for a separate
pickling step. Applicant surprisingly discovered that, in a single
step, the amount of scale and oxide on the workpiece can be
substantially reduced to an acceptable level and an iron phosphate
coating applied. By an acceptable level of oxide on the workpiece
it is meant that any remaining oxide does not interfere with
adhesion of paint applied after the phosphating step or adversely
affect corrosion resistance of the painted workpiece. Typically,
the scale and/or oxide is reduced to a smut that does not interfere
with phosphating, later paint adhesion or corrosion resistance of
the painted workpiece. Accordingly, it is an object of the
invention to provide a process for treating a ferrous metal
workpiece having laser scale and /or other ferrous oxide on at
least a portion of the workpiece comprising contacting the
workpiece with a working phosphating treatment solution of the
invention at a sufficient temperature and for a sufficient time
such that said oxide and/or scale on the workpiece are reduced to
an acceptable level and an iron phosphate coating is deposited on
the workpiece and subsequently rinsing the coated ferrous metal
workpiece.
[0009] It is another object of the invention to provide a process
for treating ferrous metal workpieces comprising removing scale
and/or oxide from the surface of the workpieces and depositing a
coating comprising iron phosphate, wherein the removing and
depositing steps take place in the same treatment bath, preferably
in the same treatment step.
[0010] It is another object of the invention to provide an aqueous
liquid concentrate that can be converted to a complete working
liquid iron phosphating composition according to the inventions by
dilution with water only.
[0011] It is yet another object of the invention to reduce the
amount of scale and/or oxide to a smut on the workpiece surface and
to coat the workpiece surface with a coating comprising iron
phosphate in a single step.
[0012] The process of the invention comprises removing undesirable
oxides, comprising ferrous oxides, from the surface of the
workpiece and forming an iron phosphate coating in a single
treatment bath, preferably in the same treatment step. Except in
the claims and the operating examples, or where otherwise expressly
indicated, all numerical quantities in this description indicating
amounts of material or conditions of reaction and/or use are to be
understood as modified by the word "about" in describing the scope
of the invention. Practice within the numerical limits stated is
generally preferred, however. Also, throughout the description,
unless expressly stated to the contrary: percent, "parts of", and
ratio values are by weight or mass; the description of a group or
class of materials as suitable or preferred for a given purpose in
connection with the invention implies that mixtures of any two or
more of the members of the group or class are equally suitable or
preferred; description of constituents in chemical terms refers to
the constituents at the time of addition to any combination
specified in the description or of generation in situ within the
composition by chemical reaction(s) between one or more newly added
constituents and one or more constituents already present in the
composition when the other constituents are added; specification of
constituents in ionic form additionally implies the presence of
sufficient counterions to produce electrical neutrality for the
composition as a whole and for any substance added to the
composition; any counterions thus implicitly specified preferably
are selected from among other constituents explicitly specified in
ionic form, to the extent possible; otherwise, such counterions may
be freely selected, except for avoiding counterions that act
adversely to an object of the invention; the term "paint" and its
grammatical variations includes any more specialized types of
protective exterior coatings that are also known as, for example,
lacquer, electropaint, shellac, porcelain enamel, top coat, base
coat, color coat, and the like; the word "mole" means "gram mole",
and the word itself and all of its grammatical variations may be
used for any chemical species defined by all of the types and
numbers of atoms present in it, irrespective of whether the species
is ionic, neutral, unstable, hypothetical or in fact a stable
neutral substance with well defined molecules; and the terms
"solution", "soluble", "homogeneous", and the like are to be
understood as including not only true equilibrium solutions or
homogeneity but also dispersions.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0013] A concentrate composition according to the invention
preferably comprises, more preferably consists essentially of, or
still more preferably consists of, water and the following
components:
[0014] (A) a component of dissolved phosphate anions;
[0015] (B) a component of sufficient dissolved acid to give the
concentrate composition itself and a working composition made by
diluting the concentrate composition with water only, an acidic pH
value and at least 20 points total acid;
[0016] (C) a component of dispersed aromatic carboxylic acid;
and
[0017] (D) a component of viscosity increasing agent that is not
part of any of components (A) through (C) as recited immediately
above; and, optionally, none, one or more of dissolved aromatic
carboxylic acid and the following components:
[0018] (E) a component of phosphating accelerator that is not part
of any of components (A) through (D) as recited immediately
above;
[0019] (F) a component of dissolved fluoride ions that are not part
of any of components (A) through (E) as recited immediately
above;
[0020] (G) a component of chelating agent that is not part of any
of components (A) through (F) as recited immediately above;
[0021] (H) a component of acidity adjustment agent that is not part
of any of components (A) through (G) as recited immediately above;
and
[0022] (J) a component of one or more surfactants that are not part
of any of components (A) through (H) as recited immediately
above.
[0023] In a composition according to the invention, component (A)
preferably, at least for economy, is sourced to a composition
according to the invention by at least one of orthophosphoric acid
and its salts of any degree of neutralization. Component (A) can
also be sourced to a composition according to the invention by
pyrophosphate and other more highly condensed phosphates, including
metaphosphates, which tend at the preferred concentrations for at
least working compositions according to the invention to hydrolyze
to orthophosphates. However, inasmuch as the condensed phosphates
are usually at least as expensive as orthophosphates, there is
little practical incentive to use condensed phosphates, except to
prepare extremely highly concentrated liquid compositions according
to the invention, in which condensed phosphates may be more
soluble.
[0024] Whatever its source, the concentration of component (A) in a
concentrate composition according to the invention, measured as its
stoichiometric equivalent as H.sub.3 PO.sub.4 with the
stoichiometry based on equal numbers of phosphorus atoms,
preferably is at least, with increasing preference in the order
given, 15, 17, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
32 or 33% and independently preferably is not more than, with
increasing preference in the order given, 60, 58, 56, 54, 52, 50,
48, 46, 44, 43, 42, 40, 39, 38, 37, 36, 35, or 34%. If the
concentration of phosphate is too low, either the shipping cost of
the concentrate will be high, because of its high water content, or
the speed of phosphating in a working composition made from the
concentrate composition generally will be slower than desirable. If
this concentration of phosphate (or any other ingredient except
water) is too high, the concentrate is more likely to become
inhomogeneous on storage for a prolonged period.
[0025] Component (B), primarily for economy, is preferably supplied
primarily by one or more of the acids listed in the description of
component (A) above. Preferred amounts of acid are most practically
specified in terms of actual or hypothetical working compositions
to be made from the concentrate compositions. In such a working
composition, it is preferred, independently for each
characteristic, that: [0026] the concentration of total acid be at
least, with increasing preference in the order given, 15, 17, 19,
20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32 or 33 points and
independently preferably is not more than, with increasing
preference in the order given, 60, 58, 56, 54, 52, 50, 48, 46, 44,
43, 42, 40, 39, 38, 37, 36, 35, or 34 points; and [0027] the pH
value of a working composition according to the invention be less
than, with increasing preference in the order given, 4.0, 3.75,
3.5, 3.25, 3.0, 2.75, 2.65, or 2.55 and more than, with increasing
preference in the order given 0, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6,
1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3 or 2.4.
[0028] ("Points" are defined for this purpose as the number of
milliliters (this unit of volume being hereinafter usually
abbreviated as "ml") of 0.10 N NaOH solution required to titrate a
10 ml sample of the composition, to a phenolphthalein or pH 8.0 end
point for total acid and a bromphenol blue or pH 3.8 end point for
free acid. If necessary because of the initial pH value of the
solution, 0.10 N strong acid titrant is substituted for the NaOH
solution and the points are then recorded as negative.)
[0029] If the total acid points are too low, the total acid will be
less effective in maintaining the desired free acid concentration
in the vicinity of the substrate being coated, where free acid is
consumed by the reactions that result in forming the phosphate
coating. If the total acid points are too high, there will be
excessive cost without any corresponding benefit and the desired
dispersion of aromatic carboxylic acid will usually be
destabilized.
[0030] If the working composition to be made from a concentrate
composition according to the invention is not otherwise specified,
a working composition made by mixing 1.0 part of the concentrate
composition with 9.0 parts of deionized water is to be used for
testing whether the concentrate composition conforms to the
preferences for acid points and pH stated above.
[0031] Component (C) of aromatic carboxylic acid preferably is
selected from acids that meet at least one, and more preferably
more than one, most preferably all, of the following criteria, each
of which is independently preferred: the molecules of the acids
contain not more than, with increasing preference in the order
given, 20, 18, 16, 14, 12, 10, 9, 8, or 7 carbon atoms each; and
the acid is soluble in pure water at 17.5.degree. C. to an extent
of at least, with increasing preference in the order given, 0.02,
0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, or 0.20 parts of
acid per 100 parts of water. The single most preferred aromatic
carboxylic acid is benzoic acid.
[0032] The concentration of aromatic carboxylic acids, including
both dispersed and dissolved acids present in a concentrate
composition according to the invention, preferably is at least,
with increasing preference in the order given, 0.5, 1.0, 1.5, 2.0,
2.5, 2.7, or 2.9% and independently preferably is not more than,
with increasing preference in the order given, 10, 8, 6.0, 5.0,
4.5, 4.0, 3.5, or 3.1%. If either the concentration of aromatic
carboxylic acid is too low, the desired benefit of protecting the
phosphated substrate against flash rusting is less likely to be
realized, while if the concentration is too high, the desired
dispersion of aromatic carboxylic acid in the concentrate
composition will usually be destabilized and/or there will be
additional cost without any offsetting benefit.
[0033] Component (D) of viscosity increasing agent may be selected
from a wide variety of viscosity increasing agents, such as natural
and synthetic poly-saccharides and derivatives thereof, latexes
incorporating a polymer with a viscosity strongly dependent on pH,
and other materials, as known in the art. Xanthan gum is most
preferred, available as Kelzan AR and ASX, from CP Kelco, Chicago
Ill., and as Rhodopol 23 and Rhodopol 50 MC from Rhodia Inc.,
Baltimore, Md. When xanthan gum is used as the only ingredient
included primarily as a viscosity increasing agent, it preferably
has a concentration in a concentrate composition according to this
invention that is at least, with increasing preference in the order
given, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.43, or
0.46% and independently preferably is not more than, with
increasing preference in the order given, 1.5, 1.0, 0.90, 0.80,
0.75, 0.71, or 0.68%. If some other viscosity modifying agent is
used, it preferably is used in a concentration to produce the same
static viscosity in the composition as is produced by one of the
above-stated preferred amounts of xanthan gum. If there is too
little viscosity increasing agent in a composition according to
this invention, the storage stability of the dispersed aromatic
carboxylic acid is greatly reduced. With too much viscosity
increasing agent, on the other hand, the concentrate would be
impracticable to use on a large scale, because of the difficulty of
pumping or otherwise efficiently moving it.
[0034] Component (E) of phosphating accelerating agent(s)
preferably is included in a concentrate composition according to
the invention, because without it the phosphating reaction in a
working composition made by diluting the concentrate composition
with water only normally will be undesirably slow. An accelerator,
which may be one or more accelerators, when present in a
concentrate composition according to the invention, preferably is
selected from the group consisting of: 6 to 80 parts of chlorate
ions per thousand parts of total working phosphating composition,
this unit of concentration being freely used hereinafter for any
constituent of any composition and being hereinafter usually
abbreviated as ppt; 1.0 to 40 ppt of m-nitrobenzene sulfonate ions;
1.0 to 40 ppt of m-nitrobenzoate ions; 1.0 to 40 ppt of
p-nitrophenol; 0.10 to 3.0 ppt of hydrogen peroxide in free or
bound form; 0.4 to 50 ppt of hydroxylamine in free or bound form;
2.0 to 100 ppt of a reducing sugar; and 20 to 600 ppt of nitrate
ions.
[0035] In one particularly preferred embodiment of the invention,
component (E) contains, preferably consists essentially of, or more
preferably consists of, two distinct subcomponents as follows:
(E.1) a subcomponent of water soluble source(s) of dissolved
hydroxylamine; and (E.2) a subcomponent of one or more dissolved
nitroaromatic organic compounds.
[0036] Subcomponent (E.1) may consist of any of hydroxylamine
itself, salts of hydroxylamine, complexes of hydroxylamine, and
even oximes, which produce hydroxylamine by hydrolysis in aqueous
solutions. Primarily for economy, safety, and convenience,
hydroxylamine sulfate is most preferred. Whatever the source of
subcomponent (E.1), its concentration, measured as its
stoichiometric equivalent as hydroxylamine, in a concentrate
composition according to the invention preferably is at least, with
increasing preference in the order given, 0.04, 0.08, 0.15, 0.20,
0.25, 0.30, 0.35, 0.38, 0.40, or 0.42% and independently preferably
is not more than, with increasing preference in the order given, 5,
3, 2.0, 1.0, 0.80, 0.70, 0.60, 0.55, 0.50, 0.47, 0.45, or 0.43%. If
the concentration of hydroxylamine is too low, the rate of
formation of the phosphating coating will be undesirably slow,
while if this concentration is too high, the cost of a composition
according to the invention will be increased without any offsetting
benefit.
[0037] The preferred choice for subcomponent (E.2), which produces
the maximum possible corrosion resistance, is meta-nitrobenzene
sulfonic acid and/or its water soluble salts, especially the sodium
salt. In a concentrate composition according to this embodiment, it
is preferred, with increasing preference in the order given, that
the concentration of subcomponent (E.2) be at least, with
increasing preference in the order given, 0.3, 0.5, 0.7, 0.90, 1.0,
1.20, 1.30, 1.40, or 1.50% and independently preferably be not more
than, with increasing preference in the order given, 10, 7, 5, 4.0,
3.0, 2.5, 2.20, 2.00, 1.90, 1.80, 1.75, 1.70, 1.65, 1.60, or 1.55%.
Whatever is used for subcomponent (E.2), if its concentration is
too low, the phosphate coating is likely to form at an
impractically slow rate from a working composition made by diluting
a concentrate composition according to the invention with water,
while if the (E.2) concentration is too high, the composition will
be excessively costly without any offsetting benefit.
[0038] The presence of optional component (F) of dissolved fluoride
in a composition according to the invention is also preferred, at
least in part because this component provides a buffering effect
for free acid concentration and usually results in better coating
quality. More preferably, this fluoride is sourced to the
composition in two differing forms: uncomplexed fluoride supplied
by hydrofluoric acid and/or one of its salts (which may be
partially or totally neutralized); and complexed fluoride supplied
by at least one of the acids HBF.sub.4, H.sub.2SiF.sub.6,
H.sub.2TiF.sub.6, H.sub.2ZrF.sub.6, and H.sub.2HfF.sub.6, and their
salts (which also may be partially or totally neutralized). Among
this group, NaBF.sub.4 is most preferred, primarily for economy and
ready commercial availability. Whatever material is used as the
source, any fluoride added from a source of complexed fluoride is
presumed, for the purpose of testing conformity with the
preferences below, to remain as complexed fluoride in the
concentrate composition, and likewise any fluoride added as
uncomplexed fluoride is assumed to remain uncomplexed in the
concentrate composition.
[0039] When both uncomplexed and complexed fluorides are present in
a concentrate phosphating composition according to the invention:
[0040] the concentration of uncomplexed fluoride in the concentrate
phosphating composition preferably is at least, with increasing
preference in the order given, 0.10, 0.20, 0.40, 0.50, 0.60, 0.70,
0.80, 0.85, 0.90, 0.95, or 0.98% and independently preferably is
not more than, with increasing preference in the order given, 10,
7, 5, 4.0, 3.0, 2.5, 2.0, 1.8, 1.6, 1.4, 1.30, 1.20, 1.10, or
1.00%; [0041] independently, the concentration of complexed
fluoride in the phosphating composition preferably is at least,
with increasing preference in the order given, 0.10, 0.20, 0.30,
0.40, 0.50, 0.60, 0.70, 0.80, 0.85, 0.87, or 0.89% and
independently preferably is not more than, with increasing
preference in the order given, 8.5, 7.5, 6.5, 5.5, 4.5, 3.5, 2.5,
2.0, 1.5, 1.3, 1.10, 1.00, 0.95, or 0.92%; and, independently, the
ratio of uncomplexed fluoride to complexed fluoride preferably is
at least, with increasing preference in the order given, 0.1:1.00,
0.3:1.00, 0.5:1.00, 0.70:1.00, 0.80:1.00, 0.90:1.00, 1.00:1.00, or
1.10:1.00 and independently preferably is not more than, with
increasing preference in the order given, 8:1.00, 6:1.00, 4:1.00,
3.0:1.00, 2.5:1.00, 2.0:1.00, 1.7:1.00, 1.50:1.00, 1.40:1.00.
1.30:1.00, 1.25:1.00, 1.20:1.00, 1.18:1.00, 1.16:1.00, 1.14:1.00,
or 1.12:1.00.
[0042] If a phosphating composition according to the invention
contains either fluoride only in uncomplexed form or fluoride only
in complexed form, the total fluoride content of the composition
preferably is at least, with increasing preference in the order
given, 0.50, 1.0, 1.3, 1.6, or 1.8% and independently preferably is
not more than, 8, 6, 4.0, 3.0, 2.5, 2.2, or 1.9%.
[0043] Component (G) of chelating agent is preferably present in a
composition according to the invention, because if it is not
present or its concentration is too low, the speed of formation of
the phosphate conversion coating with a working composition made by
diluting a concentrate composition according to the invention with
water only will usually be less than desirable and/or a large
amount of iron phosphate sludge is more likely to be formed during
use of the composition. This component (G) preferably is selected
from molecules each of which contains at least two moieties
selected from the group consisting of --COOH, --OH, and mixtures
thereof. Citric acid and gluconic acid and/or their salts are the
most preferred chelating agents. If gluconic acid or citric acid is
used, its concentration in a concentrate composition according to
the invention preferably is at least, with increasing preference in
the order given, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, or 0.16%
and independently preferably is not more than, with increasing
preference in the order given, 1.0, 0.8, 0.6, 0.40, 0.35, 0.30,
0.25, or 0.20%. If salts, mixtures, and/or other chelating agents
are used, the total concentration of component (G) is preferably
measured as its stoichiometric equivalent as gluconic acid, the
stoichiometry being based on equal numbers of chelating agent
molecules, and when so measured has the same concentration
preferences as for gluconic acid itself when used alone as
component (G).
[0044] Component (H) of acidity adjustment agent also is normally
preferably present in a composition according to the invention, if
only because it is needed in a preferred process for making a
composition according to the invention and removing it would add an
unnecessary cost. An alkali metal hydroxide is most preferred as
the alkalinizing agent, although any other sufficiently strongly
ionized source of alkalinity is suitable. The concentration,
measured as its stoichiometric equivalent as sodium hydroxide, with
the stoichiometry being based on equal content of
acid-neutralizing-alkalinity, preferably is at least, with
increasing preference in the order given, 1.0, 2.0, 3.0, 4.0, 4.5,
4.8, or 5.1% and independently preferably is not more than, with
increasing preference in the order given, 15, 12, 10, 8, 7.0, 6.5,
6.0, or 5.5%. If this concentration is either too low or too high,
already stated preferences for Total Acid, and pH of working
compositions made by diluting a concentrate composition according
to the invention with water only will not usually be obtained, and
the concentration preferences for component (H) are subordinate to
these already stated preferences.
[0045] Component (J) of one or more surfactants is preferably
included in a concentrate composition according to the invention,
at least if the working compositions made by diluting the
concentrate compositions according to the invention with water only
are to be used with little or no pre-cleaning of the substrates to
be phosphated, as is often preferred. On the other hand, if
separate cleaning processes sufficient to assure thorough
cleanliness of the substrate surfaces being phosphated are used,
the surfactants may be and preferably are omitted to reduce the
cost of the compositions. Preferred surfactants are acidified
aliphatic polyethers, such as Antarox brand products from Solvay,
Houston Tex.; alkoxylated glycols such as Triton brand products
from Dow Chemical, Midland, Mich. phosphate esters, such as
Rhodafac brand products from Rhodia, Baltimore, Md. and those shown
in the working examples.
[0046] A concentrate composition according to the invention
preferably does not develop any separation into two or more phases
that is visually detectable with unaided normal human vision within
a time interval of at least, with increasing preference in the
order given, 10, 20, 40, 80, or 150 days after it has been
manufactured.
[0047] For various reasons, almost always including at least a cost
saving from elimination of an unnecessary ingredient, it is
preferred that a composition according to this invention should be
largely free from various materials often used in prior art
compositions. In particular, compositions according to this
invention in most instances preferably do not contain, with
increasing preference in the order given, and with independent
preference for each component named, more than 5, 4, 3, 2, 1, 0.5,
0.25, 0.12, 0.06, 0.03, 0.015, 0.007, 0.003, 0.001, 0.0005, 0.0002,
or 0.0001% of each of (i) dissolved divalent cations of any of
zinc, nickel, manganese, cobalt, copper, iron, calcium, and
magnesium, (ii) dissolved cations of any kind with a valence of 3
or more, (iii) dissolved aluminum in any chemical form, and (iv)
dissolved chromium in any chemical form.
[0048] A typical process according to the invention for making a
selected mass of a concentrate composition according to the
invention having a specified concentration of each of its
ingredients, said ingredients including phosphoric acid, comprises
at least the following operations: (I) providing a first mass of
liquid that includes water, alkalinizing agent, dissolved viscosity
increasing agent and dissolved aromatic carboxylic acid, said first
mass having all of the following properties: [0049] the first mass
constitutes not more than, with increasing preference in the order
given, 95, 85, 75, 65, 60, or 50% of the selected mass of the
concentrate composition to be made; [0050] the first mass comprises
in dissolved salt form the entire content of aromatic carboxylic
acid that is to be present in both dissolved and dispersed form in
the selected mass of the concentrate composition to be made; the
first mass further comprises sufficient dissolved free alkali,
i.e., alkali in excess of any material originally added as alkali
that has reacted with any acidic material also added to or present
in said first mass of liquid, so that there is a ratio in said
first mass of moles of free alkali to moles of anions of aromatic
carboxylic acid that is at least, with increasing preference in the
order given, 0.5:1.00, 1.0:1.00, 2.0:1.00, 3.0:1.00, 3.5:1.00,
4.0:1.00, or 4.4:1.00 and independently preferably is not more
than, with increasing preference in the order given, 10:1.00,
8:1.00, 6.0:1.00, 5.5:1.00, 5.0:1.00, 4.8:1.00, or 4.6:1.00; and
(II) adding a liquid solution of phosphoric acid in water to said
first mass slowly with stirring until the entire content of
phosphoric acid to be included in the selected mass of concentrate
composition has been added to and mixed with said first mass to
form a second liquid mass.
[0051] The second liquid mass may or may not constitute the entire
selected mass of concentrate composition to be made. If it does
not, any additional ingredients needed are preferably added after
operation (II) as described above, except that: any surfactant
and/or any viscosity increasing agent that has a viscosity that
does not decrease when acidized may equally preferably be added to
the first mass or added to the second mass; and any acidic
chelating agent to be included may equally preferably be included
in the solution of phosphoric acid added during operation (II) as
described above or added to the second mass.
[0052] Additionally and independently of the other preferences and
of one another: any acid other than phosphoric acid or an aromatic
carboxylic acid preferably is added after the second mass has been
formed as described above; if hydrofluoric acid is one of the
ingredients specified for the concentrate composition, it
preferably is the last one, except possibly for water, added to the
mixture of other ingredients; any ingredient other than water that
is to be mixed into the second mass as described above preferably
is dissolved in water when it is added; and if any material is
required to be added after operation (II) as described above,
stirring of the mixture is preferably maintained continuously from
the beginning of the addition of phosphoric acid in operation (II)
until all the specified ingredients to make the specified mass of
concentrate composition have been mixed with one another.
[0053] It will be apparent to those skilled in the art that
numerous trivial variations could be made in the process sequence
as described above to achieve an equivalent result without
departing from the spirit of the invention. For example, but
without limitation: the first mass could be divided into two or
more parts, each treated in the same manner as described above for
the single first mass, and the resulting multiple second masses
could be mixed together at the end to constitute the entire
specified mass of concentrate composition; a single second mass
could be divided into two or more parts, further materials added to
at least one of the parts, and all of the resulting mixtures
combined eventually to constitute the entire specified mass of
concentrate composition; and/or operation (II) as described above
could be interrupted before all of the required phosphoric acid has
been added, then resumed later to complete operation (II).
[0054] In a process according to the invention for using a
concentrate composition according to the invention, the concentrate
is preferably diluted with an amount of water that is at least,
with increasing preference in the order given, 2, 3, 4, 5, 6, 7, 8
or 9 times its own mass to constitute a working phosphating
composition, which is then used for treating ferrous metal
workpieces to remove laser scale and/or other oxides, comprising
ferrous oxides, according to the invention.
[0055] For the particularly preferred specific embodiments as
described above: the temperature during contact between the metal
treated and a working composition made by diluting a concentrate
composition according to the invention preferably is in a range
from, with increasing preference in the order given, 21.degree. C.
to 85.degree. C., 25.degree. C. to 70.degree. C., or 30.degree. C.
to 65.degree. C.; the time of contact preferably is in a range
from, with increasing preference in the order given, 5 seconds
(hereinafter "sec") to 15 minutes (hereinafter "min"), 15 sec to 10
min, or 30 sec to 5 min; and the add-on mass of the phosphate
coating formed preferably is in a range from, with increasing
preference in the order given, 12 to 1600, 98 to 975, or 285 to
700, milligrams per square meter (hereinafter "mg/m.sup.2) of
surface treated.
[0056] For the particularly preferred specific embodiments as
described above a working phosphating composition according to the
invention preferably has a pH of less than 3 and a 25-45 total acid
points. A preferred working phosphating composition that reduces
laser scale and/or ferrous oxides on a ferrous metal substrate and
forms a phosphate conversion coating on the ferrous metal substrate
with which it is contacted, in a single step, comprises water and:
[0057] (A) 1.5% to 10% by weight dissolved phosphate ions; based on
a stoichiometric equivalent as H.sub.3PO.sub.4; (B) 20 to 50 points
of total acid; (C) 0.05% to 1.0% of at least one aromatic
carboxylic acid containing from 7 to 20 carbon atoms; and further
comprises at least one member selected from the group consisting
of: (D) 0.01 to 1.5% of xanthan gum or optionally a viscosity
modifying agent other than xanthan gum used in a concentration to
produce a same "static" viscosity of the composition as the above
stated amounts of xanthan gum; and (E) a phosphating accelerator in
an amount sufficient to provide a working solution with a
concentration of at least one member selected from the group
consisting of 0.6 ppt to 8.0 ppt of chlorate ions, 0.10 ppt to 4.0
ppt of m-nitrobenzene sulfonate ions, 0.10 ppt to 4.0 ppt of
m-nitrobenzoate ions, 0.10 ppt to 4.0 ppt of p-nitrophenol, 0.01
ppt to 0.30 ppt of hydrogen peroxide in free or bound form, 0.04
ppt to 5.0 ppt of hydroxylamine in free or bound form, 0.20 ppt to
10.0 ppt of a reducing sugar and 2.0 ppt to 60.0 ppt of nitrate
ions; (F) at least one member selected from the group consisting of
0.01% to 1.0% of uncomplexed fluoride, 0.01 to 0.85% of complexed
fluoride and mixtures thereof and wherein when both uncomplexed
fluoride and complexed fluoride are present the ratio of
uncomplexed fluoride to complexed fluoride is from 0.1:1.00 to
8:1.00 and when only uncomplexed fluoride or complexed fluoride is
present the total fluoride content of the composition is from
0.050% to 0.8%; (G) from 0.02% to 1.0% of a chelating agent wherein
the concentration is measured as its stoichiometric equivalent as
gluconic acid; (H) 0.1% to 1.5% of an acidity adjustment agent; and
(J) a component of one or more surfactants that is not part of any
of components (A) through (H).
[0058] The invention will now be further described with reference
to a number of specific examples, which are to be regarded solely
as illustrative and not as restricting the scope of the
invention.
EXAMPLES
Example 1
[0059] A typical iron phosphating bath used in the industry was
formulated for use as a comparative example. Working baths 1 and 2,
according to the invention, were formulated as shown in Table 1,
and thereafter pH adjusted by the addition of H.sub.3PO.sub.4,
only, to the desired pH level. TABLE-US-00001 TABLE 1 Aqueous
Working Bath Composition in ppt Comparative Working Working
Ingredient Bath Bath 1 Bath 2 Xanthan gum 0.15 0.50 0.50 ANTAROX
.TM. LF-330 surfactant 0.10 0.35 0.35 TRITON .TM. DF-16 surfactant
0.17 0.56 0.56 RHODAFAC .TM. RP-710 surfactant 0.53 1.75 1.75 50%
solution of NaOH in water 3.15 10.5 10.5 50% solution of gluconic
acid in 0.17 0.56 0.56 water 75% solution of H.sub.3PO.sub.4 in
water 4.62 15.4 15.4 30% solution of hydroxylamine 1.09 3.62 3.62
sulfate in water Sodium xylene sulfonate 1.05 3.50 3.50 70%
solution of HF in water 0.15 0.49 0.49 Solid NaBF.sub.4 0.11 0.35
0.35 Solid benzoic acid 0.90 3.0 3.0 pH: Examples 1 and 2 were pH
4.5 2.5 3.0 adjusted by the addition of additional amounts of
H.sub.3PO.sub.4
Example 2
[0060] Parts and panels of hot rolled steel (HRS) and cold rolled
steel (CRS) were used as substrates for this example. ACT CRS are
cold rolled steel panels that are known industry standards used for
comparative testing. Samples of both substrates were treated
according to the invention, as well as being subjected to
comparative treatments. All samples were cleaned with a
conventional alkaline cleaner, tap water rinsed, treated with a
treatment bath according to the invention or with a comparative
treatment bath, tap water rinsed and sealed with Parcolene 99, a
commercial sealant available from Henkel Corporation, and painted.
The resulting articles were subjected to salt spray testing for 500
hours according to ASTM 1654 with the results shown in Table 2.
TABLE-US-00002 TABLE 2 Salt Spray Testing of Coated Articles SALT
SPRAY ASTM 1654 (Procedure A, Method 2) Tested for 500 Hours FILM
RANGE OF MEAN THICKNESS ARTICLE** CREEP CREEP ASTM (1/1000 pH (ID)
(mm) BLISTERS (mm) RATING inch) Working 2.5 (part 3) 0 9VF 0 9 2.51
Bath 1 Working 2.5 (part 4) 0-4.0 spot 8VF 0.5 9 2.25 Bath 1
Working 3.0 (part 1) 0 9VF 0 9 2.11 Bath 2 Working 3.0 (part 5)
0-5.0 spot 8VF+ 1 8 2.04 Bath 2 Comparative 4.5 (part 2) 0-26.0 N/A
18 0 2.25 Bath Comparative 4.5 (part 6) 5.0-20.0 8VF 11 2 2.04 Bath
Working 2.5 (panel 0-0.1 spot none 0.1 9 2.71 Bath 1 9) Working 3.0
(panel 0-2.5 spot none 0.2 9 2.6 Bath 2 8) Comparative 4.5 (panel
3.0-14.5 none 11 2 2.38 Bath 7) Working 2.5(ACT 0 none 0 10 Bath 1
CRS) Working 3.0 (ACT 0 none 0 10 Bath 2 CRS) Comparative 4.5(ACT
30% none N/A 0 Bath CRS) peeling of paint **HRS unless otherwise
noted
Example 3
[0061] Paint adhesion was tested for workpieces sustaining an
impact on a cut edge. The test sample was a workpiece that included
a laser cut edge; the laser cut edge had scale resulting from the
laser cutting. HRS samples from Example 1 were subjected to impacts
perpendicular to the main plane of the part at a point on the plane
close to the laser cut edge. The impacts resulted in both
workpieces receiving a dent of approximately the same size;
workpiece A (Working Bath 2) showed no change in the paint on the
laser cut edge, workpiece B (Comparative Bath) showed delamination
of the paint on the laser cut edge along the length of the edge
that was deformed by the impact.
[0062] Table 3 shows physical data for ACT CRS test panels tested
after coating and prior to salt spray testing, showing performance
comparable to a conventional iron phosphating bath. TABLE-US-00003
TABLE 3 PHYSICAL TESTING IMPACT ARTICLES: CONCAVE CONVEX FILM
THICKNESS ACT CRS ASTM D2794 (MILS) Working Bath 1 56 4 3.8 Working
Bath 2 60 4 5.55 Comparative 68 4 3.81 Bath ACT CRS control panels
were previously tested for impact and then placed in salt spray
Example 4
[0063] Samples of ACT CRS were treated according to the invention,
as well as being subjected to comparative treatments. Working Bath
3 was the same as Working Bath 1, but was pH adjusted to pH 3.5 by
the addition of H.sub.3PO.sub.4, only. All test panels were cleaned
with a conventional alkaline cleaner, tap water rinsed, treated
with a treatment bath according to the invention or with a
comparative treatment bath, and tap water rinsed. No seal was
applied. The treated samples were subjected to salt spray according
to ASTM 1654 with the results shown in Table 4. TABLE-US-00004
TABLE 4 SALT SPRAY ASTM 1654 HRS. TESTED MEAN ASTM Treatment Bath
336 504 CREEP (mm) RATING Working Bath 1 0-1.1 s 0-3.0 0.5 9
Working Bath 2 0 0-2.1 s 0.1 9 Working Bath 3 0-0.2 s 0-2.0 s 0.2 9
Comparative Bath 2.6-5.9 5.5-12.0 6 4
[0064] Although the invention has been described with particular
reference to specific examples, it is understood that variations
and additional embodiments of the invention described herein will
be apparent to those skilled in the art without departing from the
scope of the invention as defined in the claims to follow.
* * * * *